Maybe you all know this little tip but it is something I just learned today and thought I would share it.

When using the guides to find the middle of a project if you go to View/New Guide and select the Horiz or Vert then in the little box where is says 0 in type in 50% and it will place the guide exactly down the middle. You don't have to figure out where the middle is. Sometimes when using uneven numbers it is hard to quickly find the middle. Do Horiz and then do Vert and it will place a perfect guide exactly in the middle.